The invention relates to a tensioning and sealing apparatus for strapping an object with a plastic band. More particularly, the invention is directed to a tensioning and sealing apparatus of the type that includes a housing having a tensioning unit for retaining two ends of a plastic band which are to be sealed and for tensioning the same, and having a sealing unit for connecting the two mutually overlapping ends, the tensioning unit exhibiting a tensioning shoe and a toothed tensioning wheel which is fastened on a pivotable rocker, which can be driven by a tensioning shaft, and which is intended for pressing the plastic band against the tensioning shoe and for gripping the same upon rotation.
Such an apparatus is known from the Patent Specification DE 30 13 429 C2. In this Specificaiton, the description is given of an appliance in which, after the introduction of the plastic band, with the aid of a rocking lever, a rocker, and thus a ttensioning wheel, is lowered onto the band. The tensioning wheel is then rotated by means of a rotor drive, as a result of which the band is tensioned.
The known apparatus has, inter alia, the disadvantage that the rocker, with the tensioning wheel, presses against the band and the tensioning shoe with a vastly increasing force as the band tension increases, this resulting in rapid wear of the tensioning shoe. Moreover, the tensioning unit has to be designed in a correspondingly stable, and thus heavy, manner. Furthermore, the rocker, with the tensioning wheel, is clamped fast during the tensioning process by the progressive press-on force between its bearing and the tensioning shoe, with the result that it is very difficult to release the band tensioning again without severing the band. Plastic band thus goes to waste if, for any reason, the tensioning process is not carried out satisfactorily.